Phasing mechanism



Nov, 11, 1941. A. L. HOLCOMB 2,262,141

PHASING MECHANISM Filed Oct. 12, 1959 POWER SUPPLY //v VENTOR A. L.HOLCOMB Patented Nov. 11, 1941 UNITED STATES PATENT OFFICEv PHASHVGMECHANISM Arthur L. Holcomb, Tarzana, Calif, assi'guor to ElectricalResearch Products, Inc., New York, N. Y., a corporation oi DelawareApplication October 12, 1939, Serial No. 299,063

1 Claim. (01. 112-293) This invention relates to means for establishingthe proper phase relation between a plurality oi! synchronously movingmechanisms or for restoring such relation when they get out of phase dueto some casual occurrence.

The object of the invention is to bring one of the mechanisms into thedesired phase relation with the other mechanisms by automaticallyincreasing the angle of lag of this mechanism until the mechanism isagain in phase.

A feature of the invention is a relay group actuated by the out-of-phaseindicator, to automatically. increase the angle of lag of one mechanismby an-amount determined by the relay group and not dependent upon thephase relationship at the time of the indication.

The invention is applicable to any synchronously moving mechanisms, andis particularly useful in taking motion pictures by the backgroundprojection method. In this method, in general, the background of thepicture is projected by a motion picture projector on a screen, thelocal action is enacted in front of the screen, and the background andlocal action'are photographed by one or more cameras. It is importantthat the camera shutters should only be open during the time. that .theshutter of the motion picture projector is open. Thus, the motionpicture projector and the cameras must not only run .at the same speed,but the shutters must also be in the same phase. The projector andcameras may be driven at the same speed by alternating currentsynchronous motors, or by other motors interlocked I in the usual waythrough a local circuit." The present invention is associated with theprojector and camera shutters and operates on one of the motors torestore the proper phase relation.

The single figure of the drawing shows the invention embodied in abackground projection system. .-It is, of course, evident that any ofthe' motors may be selected as the controlling motor, but, forconvenience of illustration, it will be assumed that the projector motoris controlling the camera motors, though no limitation upon the scopeofthe invention is implied by such assumption.

The shaft I is associated with theprojector, and driven at a speedhaving a known relationship with the speed and angular position of theshutter shaft. A slip ring 2 mounted on the shaft is connected to theconducting segment 3 in the insulating disc 4. The brushes 5, 5 bearrespectively upon the slip ring 2 and disc 4.

when the brush 6 is in contact with the segment 3, a circuit is closedfrom battery I through brush 5, ring 2, segment 8, brush 6, relay 8 tobattery 1, operating relay 8.

The only function of the slip ring 2, and disc 4 is to produce amomentary operation of the relay 8 at a fixed point in the revolution ofthe shaft, thus the details of this circuit closer may be widely varied.For example, the brushes 5, 6 may both bear upon the disc 4 and bemomentarily connected by the segment; 3, or two electrically connectedsegments may be used, or a projectionon the disc 4 or on the shutteritself may press two springs into contact.

The slip ring 9 and disc III are mounted on a shaft driven by the cameramotor I I. The motor II is shown driving the ring 9 and disc I8directly, but the shaft may obviously be geared to the motor or drivenin any other convenient manner. As the function of the ring 9 and discI0 is similar to the function of the ring 2 and disc 4, the details ofthis circuit closer may. also be widely varied.

If the shafts are in the proper phase relation, the segment I2 is incontact with the brush I3 at the'time that the segment 3 is in contactwith the brush 6. The relay 8 is thus operated, opening the circuit fromthe brush I3 and no adjustment takes place. 1

v .The function of the relay 8 is merely to open the circuit ofthe-brush I3 when the shafts are in'phase. If the disc 4 be made ofconducting material, and the segment 3 be made of insulating material,the relay 8 may be omitted. Other switching means may also be used toattain the same result.

When the shafts are out of phase, the brush I3 makes contact withsegment I2 when the relay 8 is not operated. A circuit is then closedfrom battery I4, through resistor I5, relay I6, contacts of relay 8,brush I3, segment I2, ring 9, brush I! to battery I4, operating relayI6, and charging the capacitor I8. The sole function of the rings,discs, segments and relay 8 is to give a momentary impulse when theshafts are out of phase, which operates relay I 6 and causes capacitorI8 to be charged. Relay It operates, opening the operating circuit atthe spring I 9.

A circuit may be traced from battery I4 through the back contact andspring 20 of relay I6, capacitor 2| back to the battery I4. Capacitor 2Iis normally charged over this circuit.

When relay It operates, the capacitor I8 discharges through relay I6'andresistor I5, holding 5 relay I 6 operated until the capacitor I8 isnearly the discharge of the capacitor 2|, which is iixed 10 by thecapacitance of the capacitor 2i and the resistance of the resistor 23.

A circuit may be traced from battery is through relay 24, springs ofrelay 22 to battery It. This circuit normally keeps the relay 2 15operated, closingthe circuit from the power supply to the motor II. whenthe relay 22 operates, it opens this circuit and releases the relay 24thus opening the circuit to the motor II. I

The circuit of the motor- II will be kept open so long as relay .2] isoperated. The relay 22 will be operated for a time determined by thedischarge of, the capacitor 2|, but can operate only once each time therelay It operates. The 25 operated during the release of relay II isdetermined by the discharge of the capacitor it. Thus, the time during20 said relay operated during the discharge of said which the circuit ofthemotor H is openis determinedonlybytherelaygroupandisnot aflected bythe degree of phase difference between the shafts. In a typical case,this time was adjusted so that the motor ll would slip back through anangle equal to about two poles.

A number of cameras may be controlled by one projector by providing aplurality of similar relay groups, all controlled by the brushes I, I.

The battery It may be replaced byany suitable source of unidirectionalcurrent, such as rectified alternating current.

What is claimed is:

In combination, aplurality of synchronously rotatable shafts, motors fordriving said shafts,

a'power circuit for one of said motors, a circuit momentarily closedwhen said shafts are out of phase, a relay operated by said closure, acapacitor associated with said relay to keep capacitor, a second relayoperatedby 881111178183, means controlled by said second relay to opensaid power source, and a second capacitor associated with said secondrelay to keep said relay harge of said capacitor.

ARTHUR L. HOLCOMIB.

